The breaking up of straight chain molecules and reforming them into new isomers with branched chains using a platinum catalyst at 450°C and 40atm

What is cracking and what are the two types of cracking?

Cracking is the breaking down of larger hydrocarbons into smaller useful ones

Two types of cracking are thermal cracking, 2000°C is required, and catalytic cracking which requires a Zeolite catalyst and 450°C temperatures

What is meant by the term "knocking"?

If the explosion in a car engine occurs too early, the pistons are jarred and makes knocking noises

What is octane rating?

An octane rating is used to indicate the proportion of branched-to-straight-chain molecules

How is octane rating measured?

The octane rating of 2, 2, 4-trimethylpentane is set at 100 whilst that of a straight chain heptane is set at 0. A fuel can be tested by comparing it with these in a test engine. The ratio of heptane : 2, 2, 4-trimethylpentane is varied in the comparator mixture until it has the same ignition properties as the sample of fuel being used. The % of the 2, 2, 4-trimethylpentane in the mixture is then taken as the octane rating of the fuel

State two methods of preventing knocking

1) Add lead (Pb(C2H5)4) to retard its ignition

2) catalytic reforming

What is an atom?

An atom is the smallest, electrically neutral, particle of an element that can take part in a chemical change

What is a molecule?

A molecule is the smallest, electrically neutral, particle of a an element or compound that can exist on its own

What is an ion?

An ion is an atom, or group of atoms, which carries an electrical charge